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In this paper, a broadband, polarization-independent metamaterial absorber for millimeter waves is proposed. Operating across the frequency range of 22.7 GHz to 37.2 GHz, our broadband, polarization-independent absorber demonstrates exceptional efficacy by capturing over 90% of incident wave power. Distinguished by an array of conductive square patches on a dielectric substrate, the proposed structure boasts a remarkably low thickness, measuring less than a quarter of the free space wavelength of the central point within its operational spectrum (excluding the ground layer thickness). Leveraging a combination of circuit modeling and transmission line theory, this paper presents the design of this absorber and also elucidates its underlying operating principles. The combination of broadband operation, low thickness, and systematic design is rarely seen in previous works. To validate the proposed approach, a physical prototype is realized using 3D printing technology, employing conductive polylactic acid (C-PLA) patches on a light polyvinyl chloride (L-PVC) substrate. The proposed absorber has various potential applications in communication, electromagnetic shielding, and satellite technologies. Finally, a comparison with recent works is performed to demonstrate the feasibility of the proposed structure for millimeter-wave applications. [ABSTRACT FROM AUTHOR]

Performance of a microwave absorbing material can be increased by moulding it into a resonator structure. These tuned structures made up of lossy materials like dielectric cavities trapped the electromagnetic waves and dissipate them. However, resonator structures are narrowband, and to make them wideband absorbers, a technique has been proposed here. In the presented work, an array of dielectric cavity resonators has been proposed having cavities of different physical dimensions. Due to change in physical dimensions, all cavities have unique resonating peaks. Arranging these cavities into two-dimensional array leads to overlapping of all the resonating peaks, and accordingly, a broadband dielectric cavity resonator (DCR) array absorber is designed. Proposed array structure has − 22.6 dB reflection coefficient and 8 GHz (6 to 14 GHz) absorption bandwidth makes it a broadband absorber which can be utilized to build an anechoic chamber for testing the electromagnetic devices. [ABSTRACT FROM AUTHOR]

Broadband optical absorbers are increasingly in demand in various applications, including solar cells and radiative cooling systems. Among various types of structures, absorbers based on metamaterial structures have attracted much attention. However, they generally suffer from the issues of narrow bandwidth, high-cost fabrication, and high sensitivity to polarization changes. This paper presents a broadband, polarization-independent metamaterial absorber working in both infrared and visible frequency regimes. This structure is composed of a continuous phase-change material film ( Ge 2 Sb 2 Te 5 ) separated between two thin spacer layers of SiO 2 , and an array of amorphous Silicon particles located on the top of the structure. The proposed device was shown to exhibit remarkable absorptivity (more than 90 percent) within a broad range of frequencies starting from 250 to 1050 THz. In addition, thanks to the structural symmetry, the strong absorbance shows a considerable overlap between transverse magnetic (TM) and transverse electric (TE) modes over an extensive range of incident angles. The designing procedure for this absorber can be used as a guideline for designing similar metamaterial absorbers in any desirable frequency band. [ABSTRACT FROM AUTHOR]

Highlights: The role of electron transport characteristics in electromagnetic (EM) attenuation can be generalized to other EM functional materials. The integrated functions of efficient EM absorption and green shielding open the view of EM multifunctional materials. A novel sensing mechanism based on intrinsic EM attenuation performance and EM resonance coupling effect is revealed. It is extremely unattainable for a material to simultaneously obtain efficient electromagnetic (EM) absorption and green shielding performance, which has not been reported due to the competition between conduction loss and reflection. Herein, by tailoring the internal structure through nano-micro engineering, a NiCo2O4 nanofiber with integrated EM absorbing and green shielding as well as strain sensing functions is obtained. With the improvement of charge transport capability of the nanofiber, the performance can be converted from EM absorption to shielding, or even coexist. Particularly, as the conductivity rising, the reflection loss declines from − 52.72 to − 10.5 dB, while the EM interference shielding effectiveness increases to 13.4 dB, suggesting the coexistence of the two EM functions. Furthermore, based on the high EM absorption, a strain sensor is designed through the resonance coupling of the patterned NiCo2O4 structure. These strategies for tuning EM performance and constructing devices can be extended to other EM functional materials to promote the development of electromagnetic driven devices. [ABSTRACT FROM AUTHOR]

We derive periodic multilayer absorbers with effective uniaxial properties similar to perfectly matched layers (PML). This approximate representation of PML is based on the effective medium theory and we call it an effective medium PML. We compare the spatial reflection spectrum of the layered absorbers to that of a PML material and demonstrate that after neglecting gain and magnetic properties, the absorber remains functional. This opens a route to create electromagnetic absorbers for real and not only numerical applications and as an example we introduce a layered absorber for the wavelength of 8 $$\upmu \hbox {m}$$ made of $$\hbox {SiO}_2$$ and NaCl. We also show that similar cylindrical core-shell nanostructures derived from flat multilayers also exhibit very good absorptive and reflective properties despite the different geometry. [ABSTRACT FROM AUTHOR]

The complex permittivity and permeability of ferrite-filled polymer composites were studied at 50 MHz to 1 GHz, and their effects on the electromagnetic compatibility (EMC) of an integrated circuit (IC) package mounted on a printed wiring board (PWB) in the far- and near-field modes were investigated. Incorporating the ferrite particles into the polymer increased the real part of the complex permeability to 10-11 at 50 MHz, and the real part exhibited a frequency dependency over the applied frequency range (50 MHz to 1 GHz). The ferrite particle increased the magnetic loss (μ″ = 3-5) as well, which can absorb the magnetic energy of the incident electromagnetic wave. By coating the test IC package with the ferrite-polymer composite materials, the EMC level of the PWB was dramatically improved. This improvement may be due to the high magnetic loss of the ferrite-polymer composite. [ABSTRACT FROM AUTHOR]